← Paradoxes & riddles
1:56
Simpson's Paradox
winning every group, losing overall
A 1986 study compared two kidney stone treatments. Treatment A worked for 81 of 87 small stones (93%) and 192 of 263 large stones (73%). Treatment B worked for 234 of 270 small stones (87%) and 55 of 80 large stones (69%). A is better for small stones AND better for large stones.
Source: A classic puzzle, retold by INFINITE SUM and fact-checked against our curated notes
Want another one?
Type the name of a paradox or riddle you've heard of, or browse the rest of the archive.